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Ditch That Pcv System Before It Is Too Late!

Discussion in 'Early CJ5 and CJ6 Tech' started by Hellion, Mar 21, 2018.

  1. Mar 21, 2018
    Hellion

    Hellion Regurgitated

    Eastern TN
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    Thanks to mickeykelley for jogging my memory with his other thread on the PCV system. Made me recall this:

    https://oppositelock.kinja.com/ditch-that-pcv-system-before-it-is-too-late-1634156554

    This is one of the best automotive articles I've ever read and it clarified to me what the modern/factory PCV system does and why it is actually not optimal for performance. The solution in a nutshell is to divert the blow-by not back into the engine, but into a catch can.

    I may not be tuning my Dauntless for maximum power and performance but I am however in general agreement with the author who says he's in favor of any enthusiast using a catch can regardless of how much or how little horsepower their car has.
    I too want to see how much blow-by is collected after 3,000 miles or so. [​IMG]

    Great comments on the article too, no idiots. Kinda of fleshes out the article in greater detail. Load them all and be sure to toggle between Staff/Community.
     
    Karl Childers likes this.
  2. Mar 21, 2018
    NCRenII

    NCRenII yellow fever

    Far Nor Cal
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    If one's installed make sure to empty it regularly and properly clean the baffle screens.
    Ordinarily I've only used them on max performance vehicles as it's under those conditions a lot of blow-by is created. THis can also be the case with engines with high mileage, poor tune, or short trips that do not fully warm up oil (to burn off moisture and unburnt fuel).
     
    Thean and Hellion like this.
  3. Mar 21, 2018
    scoutpilot

    scoutpilot Member

    Asheboro, NC
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    The PCV systems in the "L" and "F" head motors channel the blow-by into the intake manifold below and downstream from the carburetor. So no problem. Don't use one and keep a lot of kitty litter around because you'll need it to soak up the oil that is now leaking from blown seals and gaskets due to excessive crankcase pressures. Perspective gentlemen. Our old four- and six-bangers are apples and oranges when comparing to a modern motor.
     
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  4. Mar 21, 2018
    Twin2

    Twin2 not him 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Virginia Beach, VA
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    prior to PCV system . engines only had a down draft tube . so seeing oil under a old car or truck was normal back in the day
    so if it works as designed . I see no reason to eliminate it. PCV . who wants to see all that blow by when your working on engine
     
  5. Mar 21, 2018
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Hills of NH
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    Pretty tough to cause detonation in an engine designed to run on 68 octane.
     
    Last edited: Mar 21, 2018
    Hellion likes this.
  6. Mar 21, 2018
    Karl Childers

    Karl Childers Member

    Taos New Mexico
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    A few race bikes that I have built have been catch cans per track rules. A couple of Harley's I've owned have been real oil pukers and I put catch cans of my own making on those. My old trucks are road draft. The 283 in my jeep had some sort of PO Rube Goldberg attempt at a PCV that blew swarf directly into the propane atomizer. When I went back to gasoline I also went back to road draft tube on that engine.
     
    Last edited: Mar 21, 2018
  7. Mar 21, 2018
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member

    Tantallon, Nova...
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    This may be a thing on some engines but I've never seen an issue with it. I'd think that if there was enough oil getting pushed through the PCV back into the induction system to cause issues then you have bigger problems to contend with.:rolleyes:
     
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  8. Mar 21, 2018
    Karl Childers

    Karl Childers Member

    Taos New Mexico
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    The Harley Davidson Twin Cam motor is notoriously bad right from the factory. Two very large pistons and one very small crankcase make for considerable pressure even though they have made several design attempts at alleviating the problem. It isn't unusual to see oil dripping from the air cleaner on these motorcycles after they've been run hard.
     
  9. Mar 21, 2018
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member

    Tantallon, Nova...
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    O.K., but this is an early jeep tech board- unless someone has managed to re-power their CJ with a knuckle head I'm thinking it really doesn't apply. :)
     
  10. Mar 21, 2018
    Karl Childers

    Karl Childers Member

    Taos New Mexico
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    I'm working on it, I'm working on it! :D
     
  11. Mar 21, 2018
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    :susp:
     
  12. Mar 21, 2018
    Thean

    Thean Member

    HSB Idaho
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    School me here, how does venting to atmosphere - utilizing a catch can, create excess crank case pressure and blown seals?
     
  13. Mar 21, 2018
    mickeykelley

    mickeykelley Well-Known Member

    Republic of Texas
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    So I have a question in reading all this about the vent tube. On my 55 wagon with the L226, it is my understanding it has this vent tube arrangement; am I going to have an oil drip mess on the garage floor all the time once I get it all rebuilt and start parking it on cement?
     
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  14. Mar 21, 2018
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Hills of NH
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    Is there something unusual about that? :confused:
     
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  15. Mar 21, 2018
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Hills of NH
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    I'm guessing because the PCV system is under vacuum, and the can is not?
    ("Positive" crankcase ventilation…)
     
  16. Mar 22, 2018
    Mark Wahlster

    Mark Wahlster Member

    Silverton, OR
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    Just plumb it into the exhaust we did that back in the day on our hot rod chevies. The exhaust creates vacuum and draws the blow by out with the exhaust.
     
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  17. Mar 22, 2018
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    No you won't have an issue with the draft tube dripping oil. Mine doesn't....besides, everything else will leak so you will forget about the engine anyway. :D
     
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  18. Mar 22, 2018
    scoutpilot

    scoutpilot Member

    Asheboro, NC
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    The Draft Tube vents to atmosphere. The PCV system doesn't, except for that which comes out the tail pipe as burnt exhaust.
     
  19. Mar 22, 2018
    Thean

    Thean Member

    HSB Idaho
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    I don't imagine atmospheric crankcase ventilation will "damage seals and cause them to leak". Unless they were designed with the intent of having a vacuum? Although, the case could be made that putting a vacuum on the seals potentially slow leaks or causes them to leak less because of the vacuum causing a better seal to its mating/wear surface? I cant wrap my head around the amount of vacuum the PCV system actually creates. How it handles the pulses in the crankcase and if the engineers designed seal applications for the vacuum (again, how much)
    Of all the reasons a PCV system was created, was for environmental reasons. Controlling un-burned fuel and oil going to atmosphere. Potentially the other being degradation of oil from contaminants and condensate buildup. Although, why would you want to run the dirty trash back through the engine potentially creating carbon issues, etc. Seems like the reason to run it back through the system is to "burn it off"?

    1963, The PCV Valve, a "Green" Breakthrough - Generations of GM

    This is interesting:
    During World War II a different type of crankcase ventilation had to be invented to allow tank engines to operate during deep fording operations, where the normal draft tube ventilator would have allowed water to enter the crankcase and destroy the engine.[3] The PCV system and its control valve were invented to meet this need, but no need for it on automobiles was recognized. - Its Wiki so... Crankcase ventilation system - Wikipedia

    Edit: I may be getting PCV and smog pump systems conflaggled.
     
    Last edited: Mar 22, 2018
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  20. Mar 22, 2018
    montanacj

    montanacj Member

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    I’m just happy if my jeep starts
     
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